The in situ crystallization of small-grain NaY in the presence of lauryl sodium sulfate was investigated. The product containing small-grain NaY was used as a matrix to prepare REUSY catalyst via ammonium ion exchange and rare earth ion exchange. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and N-2 physical adsorption-desorption were used to characterize the samples, while the catalytic performance of prepared catalysts was evaluated by micro-activity evaluation device and advanced catalytic evaluation (ACE). It is indicated that the addition of lauryl sodium sulfate (5% of Kaolin microsphere mass) to in situ crystallization system can decrease the average grain size of the zeolite from 540 to 250 nm. Relative to the conventional in situ crystallization fluid catalytic cracking (FCC) catalysts, the catalyst prepared from in situ crystallization product containing small-grain NaY, exhibits improved performance in the conversion rate of feedstock, the selectivity of the cracking product, and the resistance to carbon deposition.